3.4.2 Variable Descriptions

A variable description defines the name, start and end column position, type, and precision for each variable. The fields in a variable description are separated by white space. Two variable descriptions are shown below with the fields indicated. Each field is then described.

Here are two example variable descriptions. Each one consists of a name, a start position, and end position, a type, and a precision.

latitude    1  10  double  6
longitude  12  22  double  6

Name

The variable name is case-sensitive, up to 63 characters long with no blanks. The variable names in the example are latitude and longitude. If the same variable is included in more than one format description within a format description file, its name must be the same in each format description.

Start Position

The column position where the first character (ASCII) or byte (binary) of a variable value is placed. The first position is 1, not 0. In the example, the variable latitude is defined to start at position 1 and longitude at 12.

End Position

The column position where the last character (ASCII) or byte (binary) of a variable value is placed. In the example, the variable latitude is defined to end at position 10 and longitude at 22.

Type

The variable type can be a standard type such as char, float, double, or a special FreeForm ND type. The type for both variables in the example is double. See Section 3.1 for descriptions of supported types.

Precision

Precision defines the number of digits to the right of the decimal point. For float or double variables, precision only controls the number of digits printed or displayed to the right of the decimal point in an ASCII representation. The precision for both variables in the example is 6.